linux-kernel - Re: [PATCH v2 06/11] memory: atmel-ebi: add DT bindings documentation

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Date:	Fri, 7 Nov 2014 16:49:40 +0100
From:	Boris Brezillon <boris.brezillon@...e-electrons.com>
To:	Rob Herring <robherring2@...il.com>
Cc:	Samuel Ortiz <sameo@...ux.intel.com>,
	Lee Jones <lee.jones@...aro.org>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Andrew Victor <linux@...im.org.za>,
	Jean-Jacques Hiblot <jjhiblot@...phandler.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Tomeu Vizoso <tomeu.vizoso@...labora.com>,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v2 06/11] memory: atmel-ebi: add DT bindings
 documentation

On Fri, 7 Nov 2014 09:21:39 -0600
Rob Herring <robherring2@...il.com> wrote:

> On Wed, Nov 5, 2014 at 10:01 AM, Boris Brezillon
> <boris.brezillon@...e-electrons.com> wrote:
> > Signed-off-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
> 
> Perhaps some commit msg?

Yes, I was just lazy and though this series would make another round
anyway :-).

I'll add a commit log to all my commits...

> 
> While this binding seems mostly okay to me, this is the 2nd memory
> controller binding I've looked at in the last day [1]. There are
> probably some others already as well. This makes me think we need a
> generic binding here. At least the node structure and how we define
> chip selects should be common.

Sure.
Any suggestion ?

BTW, I don't use any specific property to define the chip select
associated to a device, because it's already encoded in the reg
property.
TI AEMIF binding define an ti,cs-chipselect property, is there any
reason for doing that ?

Moreover, IMHO it would even make sense to have some sort of
framework/helper functions for those kind of interfaces to external
memories, but this is another story :-).

> 
> While I like timing information in time units over magic register
> values in the Tegra binding, the reality is converting timing info to
> register values is generally very hard to get both correct and
> optimal. In the end, you probably need to hand tweak the register
> settings anyway. So I'm hesitant to say it must be done 1 way here.

Well, I'm not a big fan of timings expressed in clock cycles, cause
this implies changing your DT when you tweak your master/bus clk.
Expressing those timings in nano or pico seconds let the driver figure
out what's the best value according to the current source clk rate.

Regards,

Boris


-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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